FIELD OF THE INVENTION
The invention relates to an electric power supply device for cordless power supplied units or equipment and in particular for portable equipment, such as portable hand drills and screwdrivers, electrical gardening equipment, etc. The supply device has a power storage unit connected to normally open circuit of the equipment and which at least partly supplies the working current. The storage unit is connected to a mounting support, which at least produces the electrical connecting line between the storage unit and the circuit, or even essentially mounts the complete storage unit. For producing the electrical connecting line between the mounting support and the storage unit, detachable contact pairs are provided, of which at least one comprises contacting contacts, which are arranged on the mounting support and the storage unit, the contacting contacts being provided in the vicinity of the bearing and counterbearing surfaces of the storage unit and the mounting support. The storage unit and mounting support are interconnected or detached from one another by an at least partial movement at right angles to said bearing and counterbearing surfaces.
U.S. Pat. Nos. 4,084,123 and 4,191,917 disclose supply devices, in which the box-like storage unit is so inserted in a pocket on the underside of the equipment casing, that only a relatively small part of the storage unit is exposed at the bottom. The contacting contacts of the storage unit are formed by pins projecting either upwardly or at right angles to the bearing and counterbearing surfaces, which are in linear engagement with the contacting contacts of the equipment embedded within the equipment casing and positioned above the pocket cover. The contacting contacts can be formed by leaf spring legs. The spring legs are pressed into an upright position over a relatively long spring deflection during the insertion of the storage unit, making it difficult to ensure a reliable electric contact over a large surface area. In addition, even with the storage unit removed, it is scarcely possible to check the state of the leaf spring legs. The contacting contacts of the storage unit project over the top thereof in an impeding manner and can therefore be easily damaged.
German patent 36 10 221 e.g. discloses power supply devices in which the contacting contacts are located in the vicinity of engagement surfaces of the storage unit and mounting support. However, these engagement surfaces are formed by faces located parallel to one plug-in direction of the release or insertion movement, so that it is not possible to ensure an adequate and reliable contact pressure between the contacting contacts of the contact pairs. In addition, the contacts are not readily accessible and the contacting surface is small.
Finally, e.g. French patent 22 82 324 discloses power supply devices, in which the contact pairs comprise plug pins and sockets, which require a high positional accuracy for providing a safe connection and can also be easily rendered inoperative by contamination.